Post Process AnimBPs used to be processed in the persona viewport.
This could have been intentional.
4.14 - 3249277 - NO
4.15 - 3450819 - YES
4.16 - 3466753 - YES
4.17 - 3545186 - YES
Result: Nothing happens
Expected: Cube appears attached to one of the bones (Try this repro in 4.14 to see expected)
Head over to the existing Questions & Answers thread and let us know what's up.